Coulomb screening in two dimensional materials

The rise of atomically thin two-dimensional (2D) materials provides an ultimate 2D platform for physics research and great promise of applications from their fascinating properties. With reduced dimensionality, Coulomb interaction is greatly enhanced owing to reduced dielectric screening and spatial confinement. This enhanced Coulomb interaction plays a more significant role in electronic properties of the 2D materials than their three-dimension (3D) counterparts, usually determining characteristic optical and electric properties of 2D materials.

In contrast to 3D cases where the macroscopic Coulomb screening is well described by a single macroscopic dielectric constant , more accurately a permittivity tensor in the modified Coulomb potential, the macroscopic screening in 2D dielectric cases is highly nonlocal [16–18] and the induced polarization is confined to the 2D plane, resulting in a suppression of dielectric screening in the out-of-plane direction. Apart from the polarization from periodic crystal lattice, when charge carriers and electric dipoles exist, the Coulomb interaction can be further screened. A general and specific quantitative description and comparison of the screened Coulomb potential arising from charge carriers and charge-neutral dipoles remain unclear.

In this talk, I will introduce the Coulomb interaction and Coulomb screening effect from free carriers and dipoles in two dimensional materials both experimentally and theoretically.The rise of atomically thin two-dimensional (2D) materials provides an ultimate 2D platform for physics research and great promise of applications from their fascinating properties. With reduced dimensionality, Coulomb interaction is greatly enhanced owing to reduced dielectric screening and spatial confinement. This enhanced Coulomb interaction plays a more significant role in electronic properties of the 2D materials than their three-dimension (3D) counterparts, usually determining characteristic optical and electric properties of 2D materials.

In contrast to 3D cases where the macroscopic Coulomb screening is well described by a single macroscopic dielectric constant , more accurately a permittivity tensor in the modified Coulomb potential, the macroscopic screening in 2D dielectric cases is highly nonlocal [16–18] and the induced polarization is confined to the 2D plane, resulting in a suppression of dielectric screening in the out-of-plane direction. Apart from the polarization from periodic crystal lattice, when charge carriers and electric dipoles exist, the Coulomb interaction can be further screened. A general and specific quantitative description and comparison of the screened Coulomb potential arising from charge carriers and charge-neutral

dipoles remain unclear.

In this talk, I will introduce the Coulomb interaction and Coulomb screening effect from free carriers and dipoles in two dimensional materials both experimentally and theoretically.